1. Field of the Invention
The present invention relates to a motor drive controller and a controller for controlling a motor.
2. Description of the Related Art
In common motors driven by alternately energizing their coils, electromagnetic vibration component caused by alternate energization is one of the main causes leading to vibration deterioration. It is required to solve this problem.
The vibration may be avoidable by preventing resonance at a preset range of rotation speed in normal use, for motors that are used to keep rotate in the preset range of rotation speed, but for motors, such as axial fan motor, whose vibration peaks should be suppressed below a certain value at all speeds from stop to maximum speed, the aforesaid practice is not applicable, and alternative solution.
JP-A-2011-055651 discloses a motor controller that suppresses noises due to a vibration of a stator caused by resonance with natural vibration frequency of a motor. The motor controller disclosed in JP-A-2011-055651 is provided with a rotation speed calculator for calculating rotation speeds of the motor and a modulation rate adjuster for adjusting modulation rates of an inverter based on the rotation speeds calculated by the rotation speed calculator and the natural vibration frequency of the stator. This motor controller is designed to prevent the resonance of frequency of higher harmonic frequency components with the natural frequency F of the stator, and to suppress the vibration-based noises of the stator.
The motor controller disclosed in JP-A-2011-055651 needs to adjust the modulation rates of the inverter for each frequency of the PWM signals like 180 degree energization. Therefore, a microcomputer having decent processing power is required for the motor controller, which leads to a higher cost.